One known method for abating certain diesel engine exhaust constituents is by use of an exhaust aftertreatment system that utilizes Selective Catalytic Reduction (SCR) of pollutants such as nitrogen oxides. In a typical SCR system, urea, a urea-based water solution or similar reductant solution is typically mixed with exhaust gas. In some applications, the reductant solution is injected directly into an exhaust passage through an injector device. The injected reductant solution typically mixes with exhaust gas to provide, for example, ammonia (NH3) in the exhaust stream. The ammonia then reacts with nitrogen oxides (NOx) in the exhaust in conjunction with a catalyst to provide nitrogen gas (N2) and water (H2O).
As can be appreciated, SCR systems require the presence of some form of reductant close to the engine system such that the engine can be continuously supplied during operation. Various reductant delivery systems are known and used in engine applications. In known reductant injection systems, temperature-related challenges may arise that can affect the storage of reductant.
One type of reductant is diesel exhaust fluid, which can be stored in an on-board vehicle tank, which is often made of steel. When a steel tank holding a reductant such as diesel exhaust fluid is subjected to temperatures below freezing, the reductant stored in the tank can freeze. Subsequently, the reductant can become trapped in the tank. When the trapped reductant freezes, the frozen reductant can expand, subsequently causing reductant in the tank to exert a force against the reductant tank. This expansion of the reductant may result in the tank bulging and becoming deformed, damaged, or cracked. The expansion can damage tank welds, or the like, often further damaging internal tank components.
U.S. Pat. No. 8,429,900, entitled “Liquid container for motor vehicles,” discloses a liquid container for motor vehicles, the container having an interior free space corresponding to an increase in a volume of liquid that has frozen. However, U.S. Pat. No. 8,429,900 does not address controlling reductant freezing to prevent damage to the tank.
Accordingly, what is needed is an approach to control reductant freezing in the tank in which the reductant is stored in order to prevent or limit damage to the tank.